Vision: Task Sovereignty and Multi-Layer Sync

[krisrowe]

This issue proposes a shift in how task data is managed, moving from vendor-first to sovereignty-first.

Details: docs/planned/SOVEREIGNTY.md

Key Goals:

• Data Ownership: Own the tasks locally and avoid vendor lock-in. Tasks are high-value personal data (logs/diaries).
• Long-term Preservation: Ensure data exists independent of any SaaS provider.
• Performance: Instant local search and AI integration readiness.
• Resilience: Tolerance for auth/connection issues and API changes.
• Architecture: Move toward a multi-layer sync where the vendor is just one possible UX layer.